About a week ago my electric kettle broke and I don't have the cash right now to fork out for a new one. Today, while heating water in a saucepot I recalled that I had a regular kettle somewhere, but I hadn't used it in about four years and it may have rusted. One of my roommates said that he had read once that consuming from rusty utensils and pots is okay and may even be good for you as it adds iron to your diet. He also said that there's not danger or very little.
I have read that those that use iron skillets get a lot more iron in their diet than those that do not.. which I suppose is a good thing if you have iron poor tired blood..
In addition to the link L2G posted anything with rust + is Teflon releases cancer causing nitrates. So if your kettle or any other cooking ware is made out of Teflon I certainly wouldnt cook anything very well done in it if the piece, especially if its rusty.